Promoting photocatalytic hydrogen evolution by modulating the electron-transfer in an ultrafast timescale through Mo-S₆ configuration

Maximizing ultrafast electron-transfer kinetics in semiconductor is pivotal but challenging for high-efficiency solar-to-energy during the photocatalytic reaction process due to the intrinsic property of photocatalysts with low surface electron density. Herein, a model photocatalyst CdS@Mo is synthesized through a typical hydrothermal method for modulating the ultrafast electron-transfer to enhance the surface electron density. X-ray absorption fine spectra (XAFS) reveal that Mo is coordinated with S atoms to form a Mo-S₆ configuration which is different from common MoS₂ and Mo foil structures. Based on the femtosecond transient absorption spectra (fs-TAS), it is found that the formation of Mo-S₆ configuration contributes to the fast decay of CdS signal and Mo-S₆ signal reactivation, illustrating the ultrafast electron-transfer (∼2.2 ps) from CdS to Mo-S₆ configuration, which achieves the enhanced electron density of photocatalyst surface. Finally, a holistic photocatalytic performance evaluation discloses that the growing of Mo-S₆ configuration obviously improves the photocatalytic hydrogen evolution (PHE) efficiency of CdS from 28.5 to 47.5 mmol g^–1 h^–1 with a solar-to-hydrogen (STH) efficiency of 0.10 % which is seldomly discussed in the system containing sacrificial agents. This work opens a new path to modulate the surface electron density by tuning the ultrafast electron-transfer for enhancing reaction efficiency in electron-density-dependent systems.